Automatic exhaust of high pressure lamps



Oct. 14, 1941. G. A. FREEMAN 2,259,105

AUTOMATIC EXHAUST OF HIGH PRESSURE LAMPS Filed Sept. 27, 1940 Patented Oct. i4, 194i UNITED STATES PATENT clerics azsals 1 AUTOMATIC EXHAIuaslrPoSF man ParaSemin? George A. Freeman, East Orange, N. J., assig'norV to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a

of Pennsylvania corporation The present invention relates to the evacuay tion of discharge devices and more particularly to the method and apparatus for automatically exhausting lamps of the high pressuremercury type.

It is customary in the manufacture of mercury vapor lamps to automatically exhaust the same on a machine provided with a turn-table which periodically indexes the lamp to a separate position for each step of the exhaust proci i'lcient electrical energy to the tube to cause a discharge between the electrodes while the lamp is connected to the exhaust pump. The heat generated by the discharge drives offy the occluded gases from the electrodes, which are then withdrawn by the exhaust pump. This method of exhaust is objectionable because sputtering and rvaporization of the electrodes is high at low pressure. n

A further method is to heat the electrodes by high frequency induction during one step of l automatic machine exhausting. Although such exhaust apparatus and method operates successfully for most types of lamps, it has heretofore been very inefcient in connection with high pressure lamps of the capillary type. This is due to the fact that the electrodes, which are sealed into each end of a quartz envelope, are of exceptionally small area and hence cannot conveniently be heated by high frequency induction heating to a sufficiently high temperature to completely degasify the electrodes with available apparatus.

It is accordingly an objectof the present invention to provide an automatic exhausting apparatus wherein succeeding lamps are so positioned that the electrodes can be substantially completely degasified during the exhaust process.

Another object of the present invention is the provision of an apparatus wherein succeeding lamps of the high pressure mercury vapor type can be automatically heated to a sufficiently high temperature to obtain substantially complete degasication of the electrodes.

Another object of the present invention is the provision of an automatic exhausting apparatus wherein sufciently high current is supplied to the lampto heat the electrodes lto a high temperature so as to liberate occluded gases while ,the lamp is -connected to the exhaust pump in order to completely degasify the electrodes without endangering the operation of the machine due to the high current employed.

Another object of the present invention is the provision of a method of exhausting discharge lamps ofthe high pressure type wherein the lamps are successively positioned automatically so `that the small area electrodes of such lamps are more Vcompletely degasifled than has been heretofore possible withr automatic exhaust machines. p

Still further objects `of lthe present invention will become obvious to those skilled in the art by reference to, the accompanying drawing wherein:. Y

Fig. 1 is an elevational View o f the apparatus of the present inventionras forming a part of the customary indexing exhaust machine, and

Fig. 2 is a lplan View of the apparatus as shown in Fig. 1.A

Referring now tothe drawing in detail, the apparatus shown, and'which performs the steps of the present method, comprises a standard 5 extendingA upwardly from the exhaust machine frame 6, and provided with a bracket 'I which is adjustable relative to the standard and held in place by a set screw or the like 8. The bracket 1 includes an adjustable rod or shaft 9 parallel to the, standard 5, which is likewise held in .place by av set screw I 0, and a pair of adjustable arms I Zand I3 are secured at the desired position adjacentV each end of the shaft 9 by set screws or the like I4 and I5, respectively. j

These armsIZr and I3 are formed of suitable insulating material such as Bakelite, hard rubber, or the like, and are of identical construction. As can be seen in the figures, a bolt I6 passes through the arm which serves'as a terminal for a conductor leading from a source of high frequency electrical energy and at the same time retains' a pair of fingers I1 and I3 in a position where their free ends protrude Vbeyond the' arms, with. the latter being provided with contact terminals I9 of carbon or the like, se-

-cured by rivets 20 (Fig. 2) or other suitable fastenings to the ngers.

' These fingers I1 and I8 are disposed one above the other and are normally held against a stop 22 (Fig. 2) bythe tension of fa lpair of Vcci/ l springs Sept. 12, 1939, and assigned to the same assignee as the present invention, as well as the apparatus such as shown in Patent No, 1,651,865, issued Dee cember 6, 1927, to H. D. Blake et al. and PatentV No. 1,819,597, issued August 18, 1931,'to C. Eisler.

Since such exhaust machine per se forms no part of the present invention, it is believed unnecessary that the machine be shown and described in detail herein. It should suflice to say that the indexing table, shown generally at 21, periodically rotates in the direction indicated by the arrow in Fig. 2 to successively position a high pressure mercury lamp 284m a predetermined location while the lamp is supportedv by the exhaust tubulation as shown in Figql.

When in this position, the leading-in wires for the electrodes of the lamp27 make a brushing contact with the respective ngers l1 and I8 of the arms l2 and I3, and since these are electrically connected to a source of high frequency electrical energy carried by the indexing table, the lamp is energizedby closure of a switch when desired and during the introduction of an inert gas into the envelope through the -gas port. In this position of the indexing exhaust apparatus it is essential in order to properly degasify the electrodes that they be heated very hot.` A high current will raise the temperature of the electrodes sufliciently high in a Very short period of time, but at the gas pressures ofthe inert gas heretofore used of about millimeters, sputter ing of the electrodes with attendant blackening of the envelope results.

By the exhaust method of the present invention this diiculty is overcome by the utilization of a gas pressure for the argon or similar gas as high as approximately one atmosphere (760 mm.) which enables currents to be passed offrom five to ten times normal' lamp current. This accordingly heats the electrodes to a, ver-y high temperature because sufoient energy is supplied thereto in the short indexing time,y land quickly cleans up the impurities without sputtering and blackening of the envelope.

The use of such high argon pressure during exhaust presents a problem in starting the' arc discharge, since several thousand volts are required, and if sixty cycle current. is employed, such would constitute a hazard for those working around the exhaust machine. However. such hazard is eliminated by employing high frequency current for initiating and sustaining` the discharge between thel electrodes, which high'frequency power source is carried bythe indexing machine for inductively heating the electrodes of other larger type lamps during one of the exhaust steps, and a choke coil 29 is connected in series with the source and lamp, to set the arcing current.

As the lamps are` indexed tothe position shown, they may vary inheight due. t'o variations in machine ports or length-of exhaust stem, and in order to insure contact with the lamp leads, it was found preferable to employ two, independent ngers at varying height, which.th us gives positive electrical., contact to enable arcing. of the lamp. Moreover, the carbon facings on the asesinos contact fingers eliminate the possibility of the lamp leads welding to the fingers, thus allowing the lamp to pass by the latter which yield sufciently, and then return to their normal position by virtue of the coil springs.

It thus becomes obvious to those skilled in the art that an apparatus and method of exhausting lamps of the high pressure mercury vapor type is herein provided which enables complete degasii-lcation of the electrodes during the short indexing time of an exhaust machine. Moreover, all possibility of high voltage hazards is eliminated, thus protecting the machine operator, and the apparatus when attached becomes an integral part of the exhaust machine so that succeeding lamps are treated to degasify the electrodes as a part of the exhaust during fabrication of the lamp.

Although one specic embodiment of the present invention has been shown and described, it is to be understood that other modifications thereof may be made without departing from the spirit and scope of the appended claims.

Iclaim:

1. The method of degasifying the electrodes of a discharge lamp of the high pressure mercury vapor type which comprises iilling the lamp while on an automatic exhaust machine with an inert gas at a relatively high pressure, and applying a high voltage high current to the electrodes to initiate and sustain an arc discharge therebetween to rapidly raise the electrodes to a high temperature.

2. The method of degasifying the electrodes of a discharge lamp which comprises lling the lainp while` on an automatic exhaust machine with an inert gas at a pressure of the order of one atmosphere, and applying a high frequency current tothe electrodes to initiate and sustain an arc discharge therebetween to rapidly raise the electrodes to a high temperature and drive off occluded gases.

3. The method of degasifying the electrodes of a discharge lamp in the short indexing time of an automatic exhaust machine which comprises lling `the lamp with an inert gas at a pressure of the order of one atmosphere, and applying a high voltage high current to the electrodesof suicient magnitude to ionize the gas and initiate `and sustain an arc discharge between said electrodes to rapidly heat the same to a high temperature to drive oIT` occluded gases.

LLThe method of degasifying the velectrodes of a discharge lamp, in the. short indexing time of an automatic exhaust machine which comprises iilling the lamp with an inert gas at a pressureV of the order ofA one atmosphere, and applying' a high voltage high current from a high frequency source to the electrodes to initiatc'and sustain an arc discharge therebetween to rapidly raise the electrodes to a high temperature and drive offoccluded gases.

5,.. The combination with an automatic exhaust machine provided with an indexing table for successively disposing a high pressure discharge lamp in a .predeterminedv position and having means for lling each successive lamp with an inertgasat a relatively high pressure, of a supy port carried by said exhaust machine, means seto said last-mentioned means When in engagement with the leading-in conductors of each succeeding lamp to initiate and sustain an arc discharge between the electrodes of the lamp to rapidly heat the electrodes to a high temperature and drive off occluded gases.

6. The combination with an automatic exhaust machine provided with an indexing table for successively disposing a high pressure discharge lamp in a predetermined position and having means for lling each successive lamp with an inert gas at a relatively high pressure, of a supp-ort carried by said exhaust machine, a bracket secured to said support and provided with contact terminals engaging the leading-in conductors for the electrodes of each successive lamp when disposed in said predetermined position, and means for supplying a high current to said contact terminals when in engagement with the leading-in conductors of each succeeding lamp to initiate and sustain an arc discharge between the electrodes of the lamp to rapidly heat the electrodes to a high temperature and drive off occluded gases.

7. The combination with an automatic exhaust machine provided with an indexing table for successively disposing ia high pressure discharge lamp in a predetermined position and having means for lling each successive lamp with an inert gas at a relatively high pressure, of a support carried by said exhaust machine, a bracket secured to said support and provided with spring pressed contact terminals engaging the leadingin conductors for the electrodes `of each successive lamp when disposed in said predetermined position and said contact terminals being yieldable so as not to impair movement of each lamp to a further indexing position of said machine, and a source of high frequency current connected t0 said contact terminals for initiating and sustaining an arc discharge between the electrodes of each successive lamp to rapidly heat the electrodes to a high temperature and drive oi occluded gases.

8. The combination with an automatic exhaust machine provided with an indexing table for successively disposing a high pressure discharge lamp in a predetermined position and having means for lling each successive lamp with an inert gas at a relatively high pressure, of a support carried by said exhaust machine, a bracket secured to said support and provided with spring pressed contact terminals engaging the leading-in conductors for the electrodes of each successive lamp when disposed in said predetermined position and said Contact terminals being in superimposed, pairs to insure engagement with the leading-in conductors for each of the electrodes and being yieldable so as not to impair movement of each lamp to a further indexing position of said machine, and a source of high frequency current connected to each pair of contact terminals for initiating and sustaining an arc discharge between the electrodes of each successive lamp to rapidly heat the electrodes to a high temperature and drive ofi' occluded gases.

GEORGE A. FREEMAN. 

